This invention relates to cigarette filters for tobacco smoke, and to a method for its manufacture. The filter captures gaseous, liquid, and solid waste produced by burning tobacco.
Single component fibrous cigarette filters are known in the art. These are made from viscose or cellulose acetate fibers; from natural fibers such as paper; and from polyethylene, polypropylene, or polyvinyl chloride fibers. However, these filters suffer from a number of disadvantages.
The preparation of viscose filters is expensive. The conventional production of a carded viscose sliver from the viscose staple requires a large capital investment in machinery, many labourers, and many seperate manufacturing operations. Viscose filters are heavy, they demonstrate a high resistance to the flow of gases, and they are low in filter whiteness. Chemical treatment with hardening agents is required, and the viscose fibers contain undesireable residual chemical components, such as sulphur. In addition, viscous fibers constitute a raw material for the textile industry. These fibers often cannot be replaced by synthetic fibers, despite the traditionally high cost of cellulose-based viscous fibers.
Like viscose filters, single component polypropylene or polyethylene filters are heavy and resistant to the flow of gases. The efficiency of these filters is relatively low when compared with cellulose acetate filters and with the filters of the present invention.
At present, a sliver of cellulose acetate fiber is generally considered the most suitable material for the production of cigarette filters. However, filters of this type contract during smoking, with a loss in filter volume, due to the warmth of the tobacco smoke. As it contracts, the filter shrinks from the wall of the paper wrapper, further reducing filter efficiency. In addition, the deformed filter is unappealing aesthetically. Like viscose filters, they require treatment with hardening agents.
Processes for preparing polyolefin fibers for manufacturing cigarette filters have been disclosed in the following patents: British Pat. Nos. 2,105,641; and 2,004,729; U.S. Pat. Nos. 4,189,511; 3,396,073; 3,110,642; and 3,226,795; Japanese Pat. No. 28559/70; and West German Pat. No. 2,623,844. Blends of polyolefins with other fibers for cigarette filters are disclosed in U.S. Pat. No. 3,561,361; and Belgian Pat. Nos. 884,968; and 884,967. Blends of polyester and polyamide fibers for cigarette filters are known from West German Pat. No. 2,753,789. Fibers of cellulose acetate for cigarette filters are disclosed in U.S. Pat. Nos. 3,068,837; 3,016,531; 4,411,280; and 3,079,930; and British Pat. No. 2,012,553.